Method for fabricating microstructure to generate surface plasmon waves

ABSTRACT

A method for fabricating a microstructure to generate surface plasmon waves comprises steps of: preparing a substrate, and using a carrier material to carry a plurality of metallic nanoparticles and letting the metallic nanoparticles undertake self-assembly to form a microstructure on the substrate, wherein the metallic nanoparticles are separated from each other or partially agglomerated to allow the microstructure to be formed with a discontinuous surface. The present invention fabricates the microstructure having the discontinuous surface by a self-assembly method to generate the surface plasmon waves, thus exempts from using the expensive chemical vapor deposition (CVD) technology and is able to reduce the time and cost of fabrication. The present invention also breaks the structural limitation on generation of surface plasmon waves to enhance the effect of generating the surface plasmon waves.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of co-pending application Ser. No.14/244,460, filed on 3 Apr. 2014, for which priority is claimed under 35U.S.C. §120; and this application claims priority of application Ser.No. 10/213,6489 filed in Taiwan on 9 Oct. 2013 under 35 U.S.C. §119, theentire contents of all of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a method for generating surface plasmonwaves, particularly to a method for fabricating a microstructure togenerate surface plasmon waves.

BACKGROUND OF THE INVENTION

Phenomenon of surface plasmon of metals has been widely used nowadays.Researchers find if a special metallic nanostructure is disposed on aninterface between dielectric materials, it can generate an interactionbetween electromagnetic waves and the metallic nanostructure and resultin many novel optical characteristic. The optical characteristic can becontrolled via modifying the structure, size, relative position,periodical arrangement of the metallic nanostructures and types of thedielectric materials around the metallic nanostructures. Therefore,special nanostructures can be fabricated via controlling the parametersof the metallic nanostructures to generate desired surface plasmonresonances, which can be applied in many photoelectronic products,photoelectronic measurements and academic researches. In the currentstage, the surface plasmon waves have been applied to many fields, suchas Raman spectrom measurement, thin film thickness measurement, opticsconstant measurement, solar cells, optical sensors, and biologicalsensors.

Particularly, surface plasma can also be applied to increasing the lightluminous efficiency of light emitting diode (LED). It was found that thesurface plasma effect produced at the interface between the metallicnanostructure and the dielectric material can magnify the action of theelectromagnetic field and generate near-field effect, thus enhancing theluminous efficiency of the nearby quantum dots or quantum wells andpromoting the light luminous efficiency and brightness of solid-stateLED.

Besides, light generated by recombination of electrons and holes inquantum wells is omnidirectional. Thus, only the light emitted towards adirection away from the substrate is applicable unless there is a lightguiding mechanism, and the light emitted towards the direction needs topenetrate heterogeneous layers to reach the air. During penetration,optical reaction produced inside the heterogeneous layers will cause aportion of the emitted light to be constrained inside the heterogeneouslayers and converted into another form of energy. As a result, theemitted light is decreased layer by layer. If a surface plasmonstructure is disposed on the interface between the heterogeneous layerand the air, the energy lost in the optical reaction can be easilyabsorbed and coupled. The surface plasmon structure can convert themomentum loss into photons and radiate the photons. The above-mentionedphenomenon is the so-called Localized Surface Plasmon Resonance (LSPR).

A Taiwan patent No. I395348 discloses a “Semiconductor Light EmittingElement”, which is an LED element having high light-emitting efficiencyby using the technique of surface Plasmon. It discloses a metallicsurface and a plurality of through-holes which are formed on themetallic surface and have a specified shape. Those through-holes arearranged in specified positions to form a metallic surface grating,which can excite generation of the surface plasma waves for achievingbetter light emitting efficiency.

Moreover, A Taiwan patent No. I363440 discloses “Light Emitting Element,Light Emitting Diode and Method for Fabricating the Same”. Briefly, anLED structure of this patent includes a surface plasmon coupling unit togenerate surface plasmon waves and increase the luminous efficiency ofLED.

The abovementioned conventional methods for fabricating specificnanostructures to generate surface plasma waves normally usetechnologies such as vapor deposition, sputtering coating, photo masks,pattern development and etching to form a plurality of metallicnanostructure regions, and then perform annealing process to transformthe metallic nanostructure regions into spherical structures by theeffect of surface tension. Therefore, the abovementioned conventionalmethods are complicated and expensive.

Besides, surface plasmon may be categorized into Surface PlasmonPolaritons (SPP) and Localized Surface Plasmon (LSP). The SSP exists onthe interface between a metallic material and a dielectric material,wherein the LSP exists in a metallic nanostructure by a resonance mode.So far, the conventional technology is unable to apply the SSP and theLSP techniques in an identical systematic structure. The conventionaltechnology is either unable to provide a cheaper process to generate theSSP and the LSP simultaneously.

In the conventional technology, surface plasmon can only exist in aninterface between a metallic material and a dielectric material, whichconsiderably constrains the design of surface plasmon generationstructures. Therefore, the conventional technology still has room toimprove.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to improve theconventional technology that must uses the expensive and time-consumingChemical Vapor Deposition (CVD) process to undertake the deposition of acontinuous metallic structure for generating surface plasmon waves.

Another objective of the present invention is to overcome the structurallimitation which limit the generation of surface plasmon waves byforming a 3D surface plasmon generation structure, so as to enhancefunction of the surface plasmon waves and achieve complex surfaceplasmon waves effect.

To achieve the abovementioned objectives, the present invention proposesa method for fabricating a microstructure to generate surface plasmonwaves, which comprises steps of:

Step S1: preparing a substrate; and

Step S2: using a carrier material to carry a plurality of metallicnanoparticles and letting the metallic nanoparticles undertakeself-assembly to form a microstructure on the substrate, wherein theplurality of metallic nanoparticles are separated from each other orpartially agglomerated to allow the microstructure to be formed with a“discontinuous surface”.

The present invention features in using a self-assembly method to letthe metallic nanoparticles be separated from each other or partiallyagglomerated to fabricate the microstructure with a discontinuoussurface for generating surface plasmon waves. The present invention isexempted from using the expensive CVD process and has advantages of lowfabrication cost and short fabrication time.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart of a method for fabricating a microstructure togenerate surface plasmon waves according to a first embodiment of thepresent invention.

FIGS. 2A-2D are sectional views schematically showing the steps offabricating the microstructure to generate the surface plasmon wavesaccording to the first embodiment of the present invention.

FIG. 3A is a sectional view schematically showing a microstructurefabricated according to a second embodiment of the present invention.

FIG. 3B is a sectional view schematically showing another microstructurefabricated according to the second embodiment of the present invention.

FIG. 4 is a flowchart according to a third embodiment of the presentinvention.

FIG. 5 is a SEM image of the microstructure fabricated according to thethird embodiment of the present invention;

FIG. 6 is a sectional view schematically showing the microstructurefabricated according to a fourth embodiment of the present invention;

FIGS. 7A-7E are sectional views schematically showing the steps offabricating an LED structure with the microstructure of the presentinvention;

FIG. 8 shows the I-V curves of an ordinary LED and a surface plasmon LEDfabricated according to the method of the present invention;

FIG. 9A shows light emitting efficiency curves of the ordinary LED andthe surface plasmon LED at a current of 20 mA;

FIG. 9B shows the light emitting efficiency curves of the ordinary LEDand the surface plasmon LED at a current of 350 mA; and

FIG. 10 shows light transmittance curves of microstructures fabricatedat different rotation speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described in detail in cooperation withthe drawings below.

Referring to FIGS. 1 and 2A-2D, the present invention proposes a methodfor fabricating a microstructure to generate 3 Dimensional (3D) complexsurface plasmon waves. The method of the present invention comprises thesteps of:

Step S1: preparing a substrate 10, as shown in FIG. 2A. According todifferent requirements, the substrate 10 may be a electrooptic element(such as a solar cell, an optical sensor, or an LED), a single layerfilm, or a multilayer film.

Step S2: forming a microstructure, as shown in FIG. 2B. A carriermaterial 22 is used to carry a plurality of metallic nanoparticles 21 toform a microstructure on the substrate 10 in a self-assembly way. Themetallic nanoparticles 21 are separated from each other or partiallyagglomerated to allow the microstructure to be form with a discontinuoussurface. The carrier material 22 could be a solid material, a liquidmaterial or a gaseous material. The metallic nanoparticles 21 may bemade of a material selected from a group consisting of gold, silver,aluminum, compounds thereof, alloys thereof and mixtures thereof. Themetallic nanoparticles 21 are uniformly distributed in the carriermaterial 22. In this embodiment, the concentration of the metallicnanoparticles 21 in the carrier material 22 is less than 5000 ppm, andthe metallic nanoparticles 21 are formed at a particle size rangedbetween 1 nm and 100 nm. After adding oxides and mixtures, the particlesize of the metallic nanoparticle 21 may greater than 100 nm. In thepresent invention, the discontinuous surface is formed by the metallicnanoparticles 21 that are separated from each other or partiallyagglomerated. Since that, the discontinuous surface of the presentinvention is different from the “continuous surface” formed by the CVDprocess, and the performance of the discontinuous surface is quitedifferent from the performance of the continuous surface. It should beparticularly mentioned that only the microstructure formed with thediscontinuous surface which consists of nanometric metallic particlesthat are distributed in a separated way or a partially-agglomerated waycould be realized as the microstructure to generate the surface plasmonwaves of the present invention.

In a first embodiment of the invention, the carrier material 22 is avolatile liquid such as acetone (ACE) or isopropanol (IPA), and the StepS2 further comprises the following steps of:

Step S21: spreading. The carrier material 22 and the metallicnanoparticles 21 carried by the carrier material 22 are spread on thesubstrate 10 via a spin-coating method, a spraying method, adrip-coating method, or a soaking method, as shown in FIG. 2B;

Step S22: undertaking self-assembly. The metallic nanoparticles 21 movemutually in the carrier material 22 to form a plurality of twodimensional hexagonal close packed (2D HCP) structures viaself-assembly, i.e. the metallic nanoparticles 21 are partiallyagglomerated to form a plurality of planar sheet structures.

Step S23: drying. A drying process is undertaken to gradually volatilizethe carrier material 22. Thus, the 2D HCP structures are stacked on oneanother to form a metallic particle stacking layer 20, i.e. themicrostructure with the discontinuous surface. The drying temperature isbelow 500° C., preferably between 95° C. and 170° C. The drying time isless than 1 hour, preferably between 30 seconds to 5 minutes.

In the first embodiment, the Step S21 is performed by a spin-coatingprocess. The spin-coating process can remove the residual metallicnanoparticles 21 without being arranged from the surface of a wafer andmakes the film have a uniform thickness. A film with uniform thicknesswill be obtained via spin-coating the carrier material 22 and themetallic nanoparticles 21 at an appropriate rotation speed for anappropriate time. In this embodiment, the rotation speed of thespin-coating is below 8000 rpm to allow the metallic nanoparticles 21 toform the metallic particle stacking layer 20. In fact, the rotationspeed of spin-coating correlates with the thickness and uniformity ofthe film, and the concentration of the metallic nanoparticles 21correlates with the electric properties, optical properties, electricfield and magnetic field effect and thickness.

Then, the metallic particle stacking layer 20 is used to generate thesurface plasmon waves. In order to eliminate the limitation on thegeneration of surface plasmon waves, the method of the present inventionfurther comprises:

Step S3: forming a first dielectric layer 30. As shown in FIG. 2D, thefirst dielectric layer 30 is formed on one side of the metallic particlestacking layer 20 far away from the substrate 10. The first dielectriclayer 30 is made of a material selected from a group consisting ofIndium Tin Oxide (ITO), Aluminum Zinc Oxide (AZO) and Zinc Oxide (ZnO).Afterwards, the metallic nanoparticles 21 of the metallic particlestacking layer 20 enter the first dielectric layer 30 by absorption ordiffusion to form a first particle suspension layer 40. The firstdielectric layer 30 is formed by a process such as an electron beamvapor deposition method, an ion beam vapor deposition method, a lasercoating method, an epitaxial coating method, or a plasma-enhancedchemical vapor deposition method. Thereby, some optical effect such asdiffraction, refraction and total reflection will occur at a specifiedwavelength range to form Attenuated Total Reflection (ATR), which canenhance the coupling mechanism of the surface plasmon waves.

The metallic particle stacking layer 20 and the first particlesuspension layer 40 can respectively generate the SPP and the LSP.Further, the near-field effect will cause resonance of the SPP and theLSP to enhance the surface plasmon waves, which makes the SPP and theLSP be abbreviated as SP-SP. Therefore, the metallic particle stackinglayer 20 and the first particle suspension layer 40 may serve as astructure to generate a 3D complex surface plasmon waves.

In addition to the first particle suspension layer 40 formed on the oneside of the metallic particle stacking layer 20 far away from thesubstrate 10, another particle suspension layer may also be formed onone side of the metallic particle stacking layer 20 close to thesubstrate 10 via activating the substrate 10. FIG. 3A shows a secondembodiment of the present invention, wherein the substrate 10 in theStep S1 includes a second dielectric layer 15 on the surface thereof. Inthe succeeding step of fabricating the metallic particle stacking layer20, the metallic nanoparticles 21 enter the second dielectric layer 15by absorption or diffusion, so as to form a second particle suspensionlayer 31. Alternatively, as shown in FIG. 3B, the substrate 10 isactivated via heating the substrate 10 to a temperature of 500-600° C.,or compressed with the metallic particle stacking layer 20 at atemperature of 280° C. and under a pressure of 500 Kg/cm², so that themetallic nanoparticles 21 may enter the substrate 10 to form a thirdparticle suspension layer 32. Both the second particle suspension layer31 and the third particle suspension layer 32 are formed on thesubstrate 10 to serve the same function.

In one embodiment, under one condition that the metallic particlestacking layer 20 is not formed, via adjusting the concentration of themetallic nanoparticles 21 the metallic nanoparticles 21 can enter thesubstrate 10 or the first dielectric layer 30 by absorption or diffusionto form the second particle suspension layer 31 or the first particlesuspension layer 40.

Please refer to FIG. 4 for a third embodiment of the present invention,wherein metallic spherical structures are formed. In the Step S1,preparing a substrate 10 having a plurality of grooves (not shown in thedrawings). After the Step S2, the process directly proceeds to Step S4:depositing a dielectric material on the metallic particle stacking layer20. Then, the metallic nanoparticles 21 will wrap the dielectricmaterial by self-assembly and form a plurality of spherical structureswhich are able to generate the surface plasmon waves. Refer to FIG. 5for the scanning electron microscopy (SEM) image of the sphericalstructures.

In the present invention, the metallic particle stacking layer 20 cangenerate the SPP. Also, the first particle suspension layer 40 includesthe dielectric material and the metallic nanoparticles 21 which enterthe dielectric material from the surface of the metallic particlestacking layer 20 by chemical absorption or physical diffusion, namely,in a self-assembly way. Therefore, the surface plasmon wave generated atthe first particle suspension layer 40 may be regarded as the LSP. Thus,through cooperation of the metallic particle stacking layer 20 and thefirst particle suspension layer 40 complex surface plasmon waves can begenerated. Therefore, the microstructure of the present invention cangenerate the surface plasmon waves in a coupled resonance mode of theSPP and the LSP. According to the theory of surface plasmon, a TEpolarized light is unable to generate the surface plasmon waves becauseits electric field is vertical to the incident plane, but a TM polarizedlight has a electric field parallel to the incident plane and thus it isable to form continuous waves and generate the surface plasmon waves. Assuch, lights with wavelength outside a absorption wavelength range ofthe microstructure of the invention can directly penetrate themicrostructure, and non-absorbable lights with wavelength in theabsorption wavelength range, i.e. the TE polarized light and theresidual TM polarized light that is not absorbed because of absorptionsaturation, also directly penetrates the structure. For the absorbedlights, because the metallic particle stacking layer 20 and the firstparticle suspension layer 40 of the present invention generate thesurface plasmon waves in the coupled resonance mode, they are convertedto the TE polarized light and emitted from the microstructure.

Please refer to FIG. 6 for a fourth embodiment of the present invention,in which a particle suspension structure is directly formed by modifyingthe fabrication parameters. In the Step S2, the carrier material 22 a isa non-volatile liquid that would not vaporize or volatilize. Themetallic nanoparticles 21 are uniformly distributed in the carriermaterial 22 a. The carrier material 22 a and the metallic nanoparticles21 carried by the carrier material 22 a are spread on the substrate 10via a spin-coating method, a spraying method, a drip-coating method, ora soaking method, and then the carrier material 22 a is cured via bakingor natural drying to form a nanoparticle suspension film 23, i.e. thediscontinuous surface of the microstructure of the present invention.The nanoparticle suspension film 23 fabricated thereby can also generatethe surface plasmon waves. It should be particularly mentioned that inthe third embodiment, the mutual movements of the metallic nanoparticles21 cause them to be separated from each other, so as to form thediscontinuous surface of the microstructure of the present invention.

The 3D complex surface plasmon waves generated by the abovementionedembodiments can be applied in various industries, such as to increasingthe luminous efficiency of LED and the photoelectric conversionefficiency of solar cells.

Take application of LED for instance, a light emission path of an LED isfrom the substrate 10 through the metallic particle stacking layer 20and the first particle suspension layer 40 to the first dielectric layer30. Lights passing through the light emission path can be purifiedconsecutively to increase the ratio of the TE polarized light and thelight extraction efficiency, and to decrease the structure-induced lightenergy loss. If the light emission path has a reverse sequence, it canalso achieve the same effect. Please refer to FIGS. 7A-7E. Thefabrication of a horizontal type surface plasmon LED is used toexemplify the present invention below. The process includes thefollowing steps of:

Step P1: preparing a substrate 10 a, which is an LED structure includinga substrate 11, an N-type semiconductor layer 12, an multiple quantumwell (MQW) layer 13 and a P-type semiconductor layer 14, as shown inFIG. 7A. The substrate 10 a is cleaned in this step.

Step P2: using a photolithography process and a photoresist layer 50 toform a pattern and undertaking etching to form a platform, as shown inFIG. 7B. In this step, an Inductively Coupled Plasma-Reactive IonEtching (ICP-RIE) process is used to undertake etching. Then, removingthe photoresistor layer 50 and cleaning the substrate 10 a.

Step P3: forming a coating including the metallic nanoparticles 21, asshown in FIG. 7C. The carrier material 22 and the metallic nanoparticles21 carried by the carrier material 22 are spread on the substrate 10 avia the spin-coating method, the spraying method, the drip-coatingmethod, or the soaking method. The carrier material 22 is selected froma group consisting of ACE, IPA, volatile solvents, and other solventshaving low-boiling point. The metallic nanoparticles 21 are made ofgold, silver, aluminum, or oxides thereof, and the metallicnanoparticles 21 can be a single-material type or a multi-material type.The coating is dried via baking to remove the carrier material 22 andform the metallic particle stacking layer 20.

Step P4: forming a transparent conductive layer 60 on one side of themetallic particle stacking layer 20 away from the substrate 10 a, asshown in FIG. 7D. The transparent conductive layer 60 is formed via theelectron beam vapor deposition method, the ion beam vapor depositionmethod, the laser coating method, the epitaxial coating method, or theplasma-enhanced chemical vapor deposition method. The transparentconductive layer 60 can induce some optical effect, such as diffraction,refraction and total reflection, at the specified wavelength range toform the ATR, which can enhance the coupling mechanism of the surfaceplasmon waves. In addition, the metallic nanoparticles 21 could enterthe transparent conductive layer 60 by absorption or diffusion, andthrough the self-assembly mechanism thereof to from the first particlesuspension layer 40 a on one side of the transparent conductive layer 60adjacent to the metallic particle stacking layer 20. Then, the metallicparticle stacking layer 20 cooperates with the first particle suspensionlayer 40 a to generate a complex surface plasmon wave.

Step P5: fabricating electrodes 70. As shown in FIG. 7E, two electrodes70 are respectively formed on the transparent conductive layer 60 andthe N-type semiconductor layer 12 to form the LED structure.

FIG. 8 shows curves of the current-voltage (I-V) relationships of anordinary LED 82 and a surface plasmon LED 81 fabricated according to thepresent invention and having the microstructure to generate the 3Dcomplex surface plasmon waves. It is observed that there is no muchdifference between the I-V curve of the surface plasmon LED 81 and thatof the ordinary LED 82. Please further refer to FIG. 9A and FIG. 9B forthe light emitting efficiencies which are respectively performed at acurrent of 20 mA and 350 mA. It is observed in FIG. 9A and FIG. 9B thatthe light emitting efficiency of the surface plasmon LED 81 of thepresent invention is much better than that of the ordinary LED 82. Thepresent invention indeed uses the complex surface plasmon technology toincrease the light emitting efficiency of LED.

FIG. 10 shows curves light transmittances of the microstructure of thepresent invention respect to light wavelength which also imply the lightabsorption rates. A comparison curve 91 is the transmittance-wavelengthrelationship of an LED structure unable to generate the surface plasmonwaves. A low rotation speed curve 92 is the transmittance-wavelengthrelationship of the metallic particle stacking layer 20 fabricated at alow rotation speed in the spin-coating process. A high rotation speedcurve 93 is the transmittance-wavelength relationship of the metallicparticle stacking layer 20 fabricated at a high rotation speed in thespin-coating process. The metallic particle stacking layer 20 fabricatedat the low rotation speed (the low rotation speed curve 92) has athickness greater than that of the metallic particle stacking layer 20fabricated at the high rotation speed (the high rotation speed curve93). Both the low rotation speed curve 92 and the high rotation speedcurve 93 obviously chows the same two light absorption areas L1 and L2,which respectively represent the absorption phenomena of the SPP and theLSP. Therefore, FIG. 10 indicates that the structures of the presentinvention indeed can generate both the SPP and the LSP, i.e. the presentinvention can indeed generate the 3D complex surface plasmon waves. Inthis embodiment, the low rotation speed is 2000 rpm, and the highrotation speed is 4000 rpm.

In conclusion, the present invention has the following characteristics:

-   1. The present invention does not use any expensive deposition    process but uses the self-assembly technology to form a    microstructure for generating the surface plasmon waves.-   2. The present invention uses the metallic nanoparticles of the    metallic particle stacking layer to form the first particle    suspension layer. Both the metallic particle stacking layer and the    first particle suspension layer can generate the surface plasmon    waves. Thus, the present invention can break the limitation of the    conventional structure for the generation of the surface plasmon    waves to generate the 3D complex surface plasmon waves. Therefore,    the present invention can enhance the effency of generating the    surface plasmon waves.-   3. The present invention uses the spin-coating method, the spraying    method, the drip-coating method, or the soaking method to form the    metallic particle stacking layer, whereby the succeeding first    particle suspension layer can be easily formed, so that the    fabrication cost can be effectively reduced.-   4. The present invention can vary the fabrication parameters to form    the metallic particle stacking layer, the first particle suspension    layer, the second particle suspension layer, the third particle    suspension layer, the spherical structures, or the nanoparticle    suspension film to meet different requirements.-   5. The present invention uses the coupling effect of the surface    plasmon waves to increase the output ratio of the TE polarized light    and thus can be applied in a field of filter film.-   6. The present invention can undertake an etching process together    with the spin-coating process, the spraying process, or the soaking    process, thus can greatly reduce the cost and complexity of    fabrication and has high commercial potential.-   7. The structure of the present invention can convert the light    energy, which is confined in the LED structure and unused    originally, into output light having directivity, so as to reduce    the light energy loss.-   8. The metallic particle stacking layer and the first particle    suspension layer respectively generate the SPP and the LSP. Thus,    the metallic particle stacking layer cooperates with the first    particle suspension layer to form an SP-SP structure. Therefore, the    present invention can enhance the effect of the surface plasmon    waves.-   9. The surface plasmon waves generated by the absorbed incident    light are transformed into photons. The photons are re-emitted and    mixed with the unabsorbed incident light to generate the light    mixing effect.-   10. The technique of present invention, through varying the    fabrication parameters such as the type of the solvent, the size of    particles or the concentration of particles and modifying the    environmental factors, can be used to fabricate solid-state quantum    processors, solid-state magnetic materials, or surface plasmon    photonic crystals.-   11. The microstructure of present invention be used to perform a    stripping process at an appropriate temperature through increasing    the concentration of the metallic nanoparticles in the carrier    material.-   12. The surface plasmon waves made of different metals have    different absorption and emission wavelength range. The lights    emitted by the surface plasmon waves of made one metal may serve as    incident lights and being absorbed by the surface plasmon waves made    of another metal. Furthermore, the metallic nanoparticles may be a    single-metal type or a multi-metal typeto generate the mixed light    having the required wavelength.-   13. The metallic particle stacking layer and the first dielectric    layer can be peeled off and overlay on another substrate to generate    the surface plasmon waves on another substrate.

What is claimed is:
 1. A method for fabricating a microstructure togenerate surface plasmon waves, comprising the steps of: Step S1:preparing a substrate; Step S2: using a volatile liquid to carry aplurality of metallic nanoparticles, and letting the metallicnanoparticles undertake self-assembly to form a microstructure on thesubstrate, wherein the plurality of metallic nanoparticles are separatedfrom each other or partially agglomerated to allow the microstructure tobe formed with a discontinuous surface, and wherein the Step S2 furtherincludes the steps of: Step S21: spreading the volatile liquid and themetallic nanoparticles carried by the volatile liquid on the substratevia a spin-coating method, a spraying method, a drip-coating method, ora soaking method; Step S22: letting the metallic nanoparticles movemutually in the volatile liquid to form a plurality of two dimensionalhexagonal close packed (2D HCP) structures via self-assembly; and StepS23: undertaking a drying process to gradually volatilize the volatileliquid to make the 2D HCP structures be stacked on another to form ametallic particle stacking layer serving as the discontinuous surface ofthe microstructure; and Step S3: forming a first dielectric layer on oneside of the metallic particle stacking layer far away from thesubstrate, and letting the metallic nanoparticles of the metallicparticle stacking layer enter the first dielectric layer by absorptionor diffusion to form a first particle suspension layer.
 2. The methodfor fabricating the microstructure to generate the surface plasmon wavesaccording to claim 1, wherein the volatile liquid is acetone orisopropanol.
 3. The method for fabricating the microstructure togenerate the surface plasmon waves according to claim 1, wherein thefirst dielectric layer is made of a material selected from a groupconsisting of Indium Tin Oxide (ITO), Aluminum Zinc Oxide (AZO) and ZincOxide (ZnO).
 4. The method for fabricating the microstructure togenerate the surface plasmon waves according to claim 1 furthercomprising Step S4: depositing a dielectric material on the metallicparticle stacking layer and letting the metallic nanoparticles wrap thedielectric material via self-assembly and form a plurality of sphericalstructures that is performed after the Step S2, and wherein in the StepS1, the substrate includes a plurality of grooves.
 5. The method forfabricating the microstructure to generate the surface plasmon wavesaccording to claim 1, wherein in the Step S2, the metallic nanoparticlesenter the substrate by absorption or diffusion to form a third particlesuspension layer.